title: The relationship between prenatal PCB exposure and intelligence (IQ) in 9-year-old children.
abstract: BACKGROUND
  Several epidemiologic studies have demonstrated relationships between prenatal exposure to polychlorinated biphenyls (PCBs) and modest cognitive impairments in infancy and early childhood. However, few studies have followed cohorts of exposed children long enough to examine the possible impact of prenatal PCB exposure on psychometric intelligence in later childhood. Of the few studies that have done so, one in the Great Lakes region of the United States reported impaired IQ in children prenatally exposed to PCBs, whereas another found no association.
  
  
  OBJECTIVE
  This study was designed to determine whether environmental exposure to PCBs predicts lower IQ in school-age children in the Great Lakes region of the northeastern United States.
  
  
  METHODS
  We measured prenatal exposure to PCBs and IQ at 9 years of age in 156 subjects from Oswego, New York. We also measured > 50 potential predictors of intelligence in children, including repeated measures of the home environment [Home Observation for Measurement of the Environment (HOME)], socioeconomic status (SES), parental IQ, alcohol/cigarette use, neonatal risk factors, and nutrition.
  
  
  RESULTS
  For each 1-ng/g (wet weight) increase in PCBs in placental tissue, Full Scale IQ dropped by three points (p = 0.02), and Verbal IQ dropped by four points (p = 0.003). The median PCB level was 1.50 ng/g, with a lower quartile of 1.00 ng/g and an upper quartile of 2.06 ng/g. Moreover, this association was significant after controlling for many potential confounders, including prenatal exposure to methylmercury, dichlorodiphenyldichloroethylene, hexachlorobenzene, and lead.
  
  
  CONCLUSIONS
  These results, in combination with similar results obtained from a similar study in the Great Lakes conducted 10 years earlier, indicate that prenatal PCB exposure in the Great Lakes region is associated with lower IQ in children.
authors.affiliation: Center for Neurobehavioral Effects of Environmental Toxics, State University of New York at Oswego, Oswego, New York 13126, USA. pstewar1@oswego.edu
authors.forename: Paul W
authors.initials: PW
authors.lastname: Stewart
authors.forename: Edward
authors.initials: E
authors.lastname: Lonky
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Reihman
authors.forename: James
authors.initials: J
authors.lastname: Pagano
authors.forename: Brooks B
authors.initials: BB
authors.lastname: Gump
authors.forename: Thomas
authors.initials: T
authors.lastname: Darvill
mesh_terms: D002648:Child; D015986:Confounding Factors, Epidemiologic; D004305:Dose-Response Relationship, Drug; D004781:Environmental Exposure; D004785:Environmental Pollutants / Q000633:toxicity*; D005260:Female; D006801:Humans; D007360:Intelligence / Q000187:drug effects*; D011078:Polychlorinated Biphenyls / Q000633:toxicity*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012307:Risk Factors; D012923:Social Class; D014481:United States
chemical_list: D004785:Environmental Pollutants; D011078:Polychlorinated Biphenyls